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enable -Yexplicit-nulls for scala3-library #13729

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merged 2 commits into from Nov 8, 2021
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enable -Yexplicit-nulls for scala3-library #13729

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b2d1190
enable -Yexplicit-nulls for scala3-library
olhotak Oct 8, 2021
4a1c9f2
inline mapNull to avoid creating closures
olhotak Oct 12, 2021
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31 changes: 18 additions & 13 deletions library/src/scala/IArray.scala
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Expand Up @@ -328,54 +328,59 @@ object IArray:
extension [T, U >: T: ClassTag](x: T)
def +:(arr: IArray[U]): IArray[U] = genericArrayOps(arr).prepended(x)

// For backwards compatibility with code compiled without -Yexplicit-nulls
private def mapNull[A, B](a: A, f: =>B): B =
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if((a: A|Null) == null) null.asInstanceOf[B] else f
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We can't use eq for nulls anymore?

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Apparently not. The motivation comes from:
https://contributors.scala-lang.org/t/wip-scala-with-explicit-nulls/2761/4

I don't think this was discussed widely so if people feel strongly about it, we can discuss it.

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What happens if A = X | Null (for some type X)?

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That shouldn't be a problem: an expression of type X | Null | Null is still allowed to be compared with null.


/** Conversion from IArray to immutable.ArraySeq */
implicit def genericWrapArray[T](arr: IArray[T]): ArraySeq[T] =
if arr eq null then null else ArraySeq.unsafeWrapArray(arr)
mapNull(arr, ArraySeq.unsafeWrapArray(arr))

/** Conversion from IArray to immutable.ArraySeq */
implicit def wrapRefArray[T <: AnyRef](arr: IArray[T]): ArraySeq.ofRef[T] =
// Since the JVM thinks arrays are covariant, one 0-length Array[AnyRef]
// is as good as another for all T <: AnyRef. Instead of creating 100,000,000
// unique ones by way of this implicit, let's share one.
if (arr eq null) null
else if (arr.length == 0) ArraySeq.empty[AnyRef].asInstanceOf[ArraySeq.ofRef[T]]
else ArraySeq.ofRef(arr.asInstanceOf[Array[T]])
mapNull(arr,
if (arr.length == 0) ArraySeq.empty[AnyRef].asInstanceOf[ArraySeq.ofRef[T]]
else ArraySeq.ofRef(arr.asInstanceOf[Array[T]])
)

/** Conversion from IArray to immutable.ArraySeq */
implicit def wrapIntArray(arr: IArray[Int]): ArraySeq.ofInt =
if (arr ne null) new ArraySeq.ofInt(arr.asInstanceOf[Array[Int]]) else null
mapNull(arr, new ArraySeq.ofInt(arr.asInstanceOf[Array[Int]]))

/** Conversion from IArray to immutable.ArraySeq */
implicit def wrapDoubleIArray(arr: IArray[Double]): ArraySeq.ofDouble =
if (arr ne null) new ArraySeq.ofDouble(arr.asInstanceOf[Array[Double]]) else null
mapNull(arr, new ArraySeq.ofDouble(arr.asInstanceOf[Array[Double]]))

/** Conversion from IArray to immutable.ArraySeq */
implicit def wrapLongIArray(arr: IArray[Long]): ArraySeq.ofLong =
if (arr ne null) new ArraySeq.ofLong(arr.asInstanceOf[Array[Long]]) else null
mapNull(arr, new ArraySeq.ofLong(arr.asInstanceOf[Array[Long]]))

/** Conversion from IArray to immutable.ArraySeq */
implicit def wrapFloatIArray(arr: IArray[Float]): ArraySeq.ofFloat =
if (arr ne null) new ArraySeq.ofFloat(arr.asInstanceOf[Array[Float]]) else null
mapNull(arr, new ArraySeq.ofFloat(arr.asInstanceOf[Array[Float]]))

/** Conversion from IArray to immutable.ArraySeq */
implicit def wrapCharIArray(arr: IArray[Char]): ArraySeq.ofChar =
if (arr ne null) new ArraySeq.ofChar(arr.asInstanceOf[Array[Char]]) else null
mapNull(arr, new ArraySeq.ofChar(arr.asInstanceOf[Array[Char]]))

/** Conversion from IArray to immutable.ArraySeq */
implicit def wrapByteIArray(arr: IArray[Byte]): ArraySeq.ofByte =
if (arr ne null) new ArraySeq.ofByte(arr.asInstanceOf[Array[Byte]]) else null
mapNull(arr, new ArraySeq.ofByte(arr.asInstanceOf[Array[Byte]]))

/** Conversion from IArray to immutable.ArraySeq */
implicit def wrapShortIArray(arr: IArray[Short]): ArraySeq.ofShort =
if (arr ne null) new ArraySeq.ofShort(arr.asInstanceOf[Array[Short]]) else null
mapNull(arr, new ArraySeq.ofShort(arr.asInstanceOf[Array[Short]]))

/** Conversion from IArray to immutable.ArraySeq */
implicit def wrapBooleanIArray(arr: IArray[Boolean]): ArraySeq.ofBoolean =
if (arr ne null) new ArraySeq.ofBoolean(arr.asInstanceOf[Array[Boolean]]) else null
mapNull(arr, new ArraySeq.ofBoolean(arr.asInstanceOf[Array[Boolean]]))

/** Conversion from IArray to immutable.ArraySeq */
implicit def wrapUnitIArray(arr: IArray[Unit]): ArraySeq.ofUnit =
if (arr ne null) new ArraySeq.ofUnit(arr.asInstanceOf[Array[Unit]]) else null
mapNull(arr, new ArraySeq.ofUnit(arr.asInstanceOf[Array[Unit]]))

/** Convert an array into an immutable array without copying, the original array
* must _not_ be mutated after this or the guaranteed immutablity of IArray will
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4 changes: 2 additions & 2 deletions library/src/scala/reflect/Selectable.scala
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Expand Up @@ -21,7 +21,7 @@ trait Selectable extends scala.Selectable:
final def selectDynamic(name: String): Any =
val rcls = selectedValue.getClass
try
val fld = rcls.getField(name)
val fld = rcls.getField(name).nn
ensureAccessible(fld)
fld.get(selectedValue)
catch case ex: NoSuchFieldException =>
Expand All @@ -35,7 +35,7 @@ trait Selectable extends scala.Selectable:
*/
final def applyDynamic(name: String, paramTypes: Class[_]*)(args: Any*): Any =
val rcls = selectedValue.getClass
val mth = rcls.getMethod(name, paramTypes: _*)
val mth = rcls.getMethod(name, paramTypes: _*).nn
ensureAccessible(mth)
mth.invoke(selectedValue, args.asInstanceOf[Seq[AnyRef]]: _*)

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10 changes: 5 additions & 5 deletions library/src/scala/runtime/LazyVals.scala
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Expand Up @@ -5,21 +5,21 @@ package scala.runtime
*/
object LazyVals {
private[this] val unsafe: sun.misc.Unsafe =
classOf[sun.misc.Unsafe].getDeclaredFields.find { field =>
field.getType == classOf[sun.misc.Unsafe] && {
field.setAccessible(true)
classOf[sun.misc.Unsafe].getDeclaredFields.nn.find { field =>
field.nn.getType == classOf[sun.misc.Unsafe] && {
field.nn.setAccessible(true)
true
}
}
.map(_.get(null).asInstanceOf[sun.misc.Unsafe])
.map(_.nn.get(null).asInstanceOf[sun.misc.Unsafe])
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.nn.get(null) reads strange to me - it looks redundant contradictory?

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Here classOf[sun.misc.Unsafe].getDeclaredFields.nn is an Array[Field | Null] and then after calling find is an Option[Field | Null], so calling map would require asserting the inner value is also not null

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.map is being called on Option[Field | Null].

The type of _ is thus Field | Null.

The type of _.nn is thus java.lang.reflect.Field. This type has a get(Object) method to read the value of the field. The API of this method says that for a static field, the parameter of type Object is ignored and should be null.

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OK, thanks for the explanation!

.getOrElse {
throw new ExceptionInInitializerError {
new IllegalStateException("Can't find instance of sun.misc.Unsafe")
}
}

private[this] val base: Int = {
val processors = java.lang.Runtime.getRuntime.availableProcessors()
val processors = java.lang.Runtime.getRuntime.nn.availableProcessors()
8 * processors * processors
}
private[this] val monitors: Array[Object] =
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3 changes: 2 additions & 1 deletion library/src/scala/runtime/Scala3RunTime.scala
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Expand Up @@ -15,7 +15,8 @@ object Scala3RunTime:
* Extracted to minimize the bytecode size at call site.
*/
def nn[T](x: T | Null): x.type & T =
if (x == null) throw new NullPointerException("tried to cast away nullability, but value is null")
val isNull = x == null
if (isNull) throw new NullPointerException("tried to cast away nullability, but value is null")
Comment on lines -18 to +19
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What is the benefit of this change?

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A workaround for #7882

else x.asInstanceOf[x.type & T]

end Scala3RunTime
4 changes: 2 additions & 2 deletions library/src/scala/util/FromDigits.scala
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Expand Up @@ -135,7 +135,7 @@ object FromDigits {
case ex: NumberFormatException => throw MalformedNumber()
}
if (x.isInfinite) throw NumberTooLarge()
if (x == 0.0f && !zeroFloat.pattern.matcher(digits).matches) throw NumberTooSmall()
if (x == 0.0f && !zeroFloat.pattern.matcher(digits).nn.matches) throw NumberTooSmall()
x
}

Expand All @@ -153,7 +153,7 @@ object FromDigits {
case ex: NumberFormatException => throw MalformedNumber()
}
if (x.isInfinite) throw NumberTooLarge()
if (x == 0.0d && !zeroFloat.pattern.matcher(digits).matches) throw NumberTooSmall()
if (x == 0.0d && !zeroFloat.pattern.matcher(digits).nn.matches) throw NumberTooSmall()
x
}

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1 change: 1 addition & 0 deletions project/Build.scala
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Expand Up @@ -791,6 +791,7 @@ object Build {
(Compile / scalacOptions) ++= Seq(
// Needed so that the library sources are visible when `dotty.tools.dotc.core.Definitions#init` is called
"-sourcepath", (Compile / sourceDirectories).value.map(_.getAbsolutePath).distinct.mkString(File.pathSeparator),
"-Yexplicit-nulls",
),
)

Expand Down